The present invention relates to polyurethaneureas which are soluble in amide solvents and which are prepared from a polymeric glycol, at least one alkyl substituted 1,1xe2x80x2-methylenebis(4-isocyanatobenzene), and at least one doubly-hindered diamine. The present invention also relates to segmented polyurethaneurea fibers, dry-spun or wet-spun, comprising such polyurethaneureas and having superior whiteness retention, heat-set efficiency, and low percent set.
For the sake of convenience, and not of limitation, the present invention herein is discussed in terms of spandex, but should be construed to include all embodiments described in the following disclosure and equivalents.
Spandex has found widespread use in the apparel industry, such as in hosiery, foundation garments and sportswear where an elastic polymer imparts beneficial properties. Spandex is susceptible to discoloration under certain environmental conditions, for example in the presence of elevated temperatures and atmospheric gases such as nitrogen dioxide. The thermal stability of spandex is of particular interest because spandex-containing fabrics and garments are typically heat-set to provide dimensional stability and to shape the finished garment. In the manufacture of tricot knits and women""s hosiery, for example, spandex is often knit into the fabric with nylon. After knitting, the fabric is frequently heat-set to remove wrinkles and stabilize the dimensions of the fabric. Typical heat-setting temperatures used in commercial operations are 195xc2x0 C. for fabrics containing spandex and 6,6-nylon, 190xc2x0 C. when the fabric contains 6-nylon, and 180xc2x0 C. when the fabric contains cotton. It is also desirable to heat-set fabrics containing cotton and spandex, but if the spandex has adequate heat-set efficiency only at temperatures used for nylon- containing fabrics, the spandex cannot be properly heat-set in cotton-containing fabrics, which will be damaged by exposure to the required high temperatures. Improved heat-setting efficiency is desirable to save energy and improve productivity, and reduced discoloration by heat is desirable to provide an improved appearance. It is desirable, therefore, to prepare a spandex having a combination of good environmental resistance (xe2x80x9cwhiteness retentionxe2x80x9d) and high heat-set efficiency thus saving energy and improving productivity, especially if the mechanical properties of the spandex are not adversely affected.
A variety of methods have been used to improve the heat-set efficiency of spandex and thereby lower the temperature at which the spandex can be heat-set. For example, the use of 15-32 mole percent of 2-methyl-1,5-pentanediamine as a coextender in making spandex is disclosed in U.S. Pat. No. 4,973,647,but such low levels do not provide spandex with sufficiently high heat-set efficiency at the moderate temperatures permitted for fabrics containing cotton. U.S. Pat. Nos. 5,000,899, 5,948,875 and 5,981,686 disclose the use of high proportions of 2-methyl-1,5pentanediamine and 1,3-diaminopentane chain extender, respectively, to increase the heat-set efficiency of spandex, but using such large amounts of co-extender can add to the cost of the fiber. U.S. Pat. No. 5,539,037 discloses the use of low concentrations of alkali metal carboxylates and thiocyanate in spandex to increase its heat-set efficiency. However, such salts can be removed by dissolution during fabric processing, and their effectiveness can thereby be reduced. Japanese Published Patent Applications JP07-82608, JP08-020625, JP08-176253,and JP08-176268 and U.S. Pat. Nos. 3,631,138 and 5,879,799 disclose the use of various levels of isocyanato-2-[(4xe2x80x2-isocyanatophenyl)methyl]benzene. The properties of spandex made from such compositions, however, do not have the desired combination of high heat-set efficiency, elongation, and unload power.
The use of substituted diisocyanates in the preparation of segmented polyurethanes for spandex has been reported. British Patent Number 1,102,819 discloses the preparation of spandex using methyl-and ethyl-substituted 4,4xe2x80x2-methylenebis(2,6-dimethylphyenyl)diisocyanates in combination with polytetramethyleneether glycol. The resulting xe2x80x9ccappedxe2x80x9d glycols were then reacted with conventional chain extenders such as ethylenediamine, 2-methyl-1,5-pentamethylenediamine, propylenediamine, and the like. The polyurethaneureas prepared by this reaction, however, are insufficiently soluble to be commercially useful in making spandex by dry-spinning or wet-spinning from solution. International Published Patent Application, WO 96/05171 discloses the use of 4,4xe2x80x2-methylene-bis-(3-chloro-2,6-dialkylphenylisocyanates) in coatings as a less toxic replacement for toluene-2,4-diisocyanate. However, polyurethane polymers prepared from this diisocyanate and the polymeric glycols and diamine chain extenders suitable for making spandex, do not have the necessary solubility for spinning spandex from amide solvents.
There is a need for polyurethaneureas which are sufficiently soluble to be used for dry-spinning and/or wet-spinning spandex with improved whiteness retention, heat-set efficiency, and low percent set.
The present invention relates to a polyurethaneurea comprising the reaction product of a polymeric glycol, at least one Orthoalkyl-MDI, and a diamine chain extender composition comprising at least one bulky diamine. The Orthoalkyl-MDI according to the present invention are shown in Formula I: 
wherein:
each R1 may be the same or different and are independently selected from hydrogen, methyl, ethyl, propyl or isopropyl;
each R2 may be the same or different and are independently selected from hydrogen, methyl, ethyl, propyl or isopropyl; and
each X may be the same or different and are selected from hydrogen, fluorine, or chlorine, preferably hydrogen or chlorine.
Unless otherwise indicated, as used herein the term, xe2x80x9cAmide solublexe2x80x9d means that the polyurethaneurea is capable of being dissolved in at least one amide solvent to form a spinnable solution.
1,3-BAMCH refers to 1,3-bis(aminomethyl)cyclohexane;
xe2x80x9cBulky diaminexe2x80x9d refers to a chain extender diamine sterically hindered at both amine groups;
1,4-DAB refers to 1,4-diaminobutane;
1,2-DACH refers to 1,2-diaminocyclohexane;
1,3-DACH refers to 1,3-diaminocyclohexane;
DCTEMDI refers to bis(2-chloro-3,5-diethyl-4-isocyanatophenyl)methane;
DEA refers to diethylamine;
DIDMMDI refers to bis(3-isopropyl-4-isocyanato-5-methylphenyl)methane;
DIMDI refers to bis(3-isopropyl-4-isocyanatophenyl)methane;
DMAc refers to N,N-dimethylacetamide;
DMDEMDI refers to bis(3-methyl-4-isocyanato-5-ethylphenyl)methane;
EDA refers to ethylenediamine;
MDI refers to 4,4xe2x80x2-diphenylmethane diisocyanate;
MPMD refers to 2-methyl-1,5-pentanediamine;
NPDA refers to neopentylenediamine (2.2xe2x80x2-dimethyl-1,3-diaminopentane);
xe2x80x9cOrthoalkyl-MDIxe2x80x9d refers to a diisocyanate having two or more alkyl groups of one to three carbon atoms on the positions ortho to the isocyanate groups (the 3,5-positions), optionally substituted with one or more halogens;
1,2-PDA refers to 1,2-diaminopropane;
1,3-PDA refers to 1,3-diaminopropane;
PO4G refers to poly(tetramethyleneether) glycol;
PO(4G/2Me4G) refers to poly(tetramethyleneether-co-2-methyltetramethyleneether) glycol;
xe2x80x9cSpandexxe2x80x9d refers to manufactured fiber in which the fiber-forming substance is a synthetic polyrner comprised of at least 85% of a segmented polyurethane (16 C.F.R. xc2xa7 303.7(k), Federal Trade Commission)
TEMDI refers to bis(3,5-diethyl-4-isocyanatophenyl)methane;
TIMDI refers to bis(3,5-diisopropyl-4-isocyanatophenyl)methane; and
TMMDI refers to bis(3,5-dimethyl-4-isocyanatophenyl)methane.
It has now been unexpectedly found that the whiteness retention, heat-set efficiency and percent set are improved when spandex comprises the reaction product of a polymeric glycol, at least one diisocyanate having two or more alkyl groups of one to three carbon atoms on the positions ortho to the isocyanate groups (the 3,5-positions) and a composition comprising at least one bulky diamine. As heat-set temperature rises, so too does heat-set efficiency, and the improvement observed in the spandex of the invention is useful and advantageous both: (i) at the low heat-set temperatures typical for fabrics containing spandex and cotton or wool; and (ii) at the higher temperatures used for fabrics containing spandex and hard fibers, such as nylon. The polyurethaneureas of the present invention have unexpectedly good solubility in amide solvents, and spandex spun from these polymers has unexpectedly good resistance to environmental conditions.
Polymers useful in this invention are customarily prepared by reacting a di-functional polymer, such as a polymeric glycol, with a diisocyanate to form a mixture of isocyanate-terminated prepolymer and unreacted diisocyanate (xe2x80x9ccapped glycolxe2x80x9d). The capped glycol can be dissolved in a suitable solvent such as dimethylacetamide, dimethylformamide, or N-methylpyrrolidone, and then reacted with a difunctional chain extender composition to form a polyurethaneurea solution. If desired, dibutyltin dilaurate, stannous octoate, mineral acids, tertiary amines such as triethylamine, N,Nxe2x80x2-dimethylpiperazine, and the like, or other known catalysts can be used to increase the rate of capping and chain extension. Such polyurethaneureas are termed xe2x80x9csegmentedxe2x80x9d because they are comprised of xe2x80x9chardxe2x80x9d urethane and urea segments derived from the diisocyanate and chain extender and xe2x80x9csoftxe2x80x9d segments derived primarily from the polymeric glycol. The solubility of the polyurethaneurea is important because insolubles such as xe2x80x9cgelsxe2x80x9d can hinder commercial spandex production which is typically accomplished using dry-spinning or wet-spinning techniques.
Polymeric glycols used in the preparation of the polyurethanes can include polyether glycols, polyester glycols and polycarbonate glycols. Useful polymeric glycols can include, but are not limited to, poly(trimethyleneether) glycol, poly(tetramethyleneether) glycol, poly(tetramethylene-co-2-methyl-tetramethyleneether) glycol, poly(ethylene-co-tetramethyleneether) glycol, poly(propylene-co-tetramethyleneether) glycol, poly(ethyleneco-butylene adipate) glycol, poly(2,2-dimethyl-1,3-propylene dodecanedioate) glycol, poly(3-methyl-1,5-pentamethylene dodecanedioate) glycol, poly(pentane-1,5-carbonate) glycol, and poly(hexane-1,6-carbonate) glycol. When poly(tetramethylene-co-2-methyl-tetramethyleneether) glycol is used, the 2-methyltetramethyleneether moiety can be present in the range of about 4 to about 20 mole percent. Preferably, the polymeric glycol is a polyether glycol, more preferably poly(tetramethyleneether) glycol or poly(tetramethyleneether-co-2-methyltetramethyleneether) glycol.
In the preparation of the polyurethaneurea of the present invention, at least one Orthoalkyl-MDI must be used. Such Orthoalkyl-MDI includes, but is not limited to, TMMDI, DIDMMDI, TEMDI, TIMDI, DIMDI, DCTEMDI, DMDEMDI, and the like. Preferred Orthoalkyl-MDI is TMMDI and TEMDI, more preferably, TEMDI.
The polyurethaneurea can comprise the reaction product of a polymeric glycol, one or more Orthoalkyl-MDI in combination with MDI, and a bulky diamine. The total amount of Orthoalkyl-MDI is at least about 20 mole percent of total diisocyanates, preferably at least about 60 mole percent of the total diisocyanates. In one embodiment, the composition of diisocyanates comprises only Orthoalkyl-MDI. In making the capped glycol, the diisocyanate(s) can be added all at once or in two or more steps and in any order.
For the polyurethaneurea to have sufficient solubility in amide solvents to spin spandex from the polymer solution, the diamine chain extender composition must comprise at least one bulky diamine. Examples of bulky diamines include NPDA, 2,5-dimethyl-2,5-hexanediamine, 2,5-dimethylpiperazine, 2,3,5,6-tetramethyl-1,4-diaminocyclohexane, and the like. NPDA is preferred.
The bulky diamine is present to an extent of at least about 80 mole percent, and preferably at least about 90 mole percent, of the total diamine chain extender composition, any remaining diamine being selected from conventional diamine chain extenders such as ethylenediamine, 1,3-diaminocyclohexane, 1,1xe2x80x2-methylenebis(4-aminocyclohexane), 2-methyl-1,5-diaminopentane, 1,3-diaminopentane, and 1,2-diaminopropane, and the like, and mixtures thereof. Optionally, a chain terminator, for example diethylamine, cyclohexylamine, or n-hexylamine can be used to control the molecular weight of the polymer, and small amounts of tri-functional compounds such as diethylenetriamine can be used to help control solution viscosity.
In a preferred embodiment, the polyurethaneurea comprises the reaction product of PO4G or PO(4G/2Me4G), at least about 60 mole percent TMMDI, TEMDI, or mixtures thereof, and optionally MDI, and a mixture of chain extenders comprising at least about 90 mole percent neopentylene diamine.
In an alternate embodiment, the polyurethaneurea can be the reaction product of PO4G, a mixture of diisocyanates comprising MDI and an Orthoalkyl-MDI selected from TIMDI and TEMDI, the mole ratio of Orthoalkyl-MDI to MDI being at least 20/80,and a diamine chain extender composition comprising NPDA.
The spandex can contain additives such as stabilizers and pigments, provided such additives do not detract from the benefits of the invention. Among such additives are benzotriazole-based stabilizers, ultraviolet light absorbers, other light resistance agents, antioxidants, delustrants, anti-tack agents, dyes and dye enhancers, lubricants such as mineral oil and silicone oils, deodorants, and antistatic agents. Other examples of additives include Methacrol(copyright) 2462 (a registered trademark of E.I. du Pont de Nemours and Company, a polymer of bis(4-isocyanatocyclohexyl)methane and 3-t-butyl-3-aza-1,5-pentanediol), titanium oxide, zinc oxide, magnesium stearate, barium sulfate, hydrotalcite, mixtures of huntite and hydromagnesite, bactericides containing silver, zinc, or compounds thereof, and the like.
Strength and elastic properties of the spandex were measured in accordance with the general method of ASTM D 2731-72. For the examples reported in Tables 2 and 3 below, spandex filaments having a 5 cm gauge length were cycled between 0% and 300% elongation at a constant elongation rate of 50 cm per minute. Load Power (xe2x80x9cLPxe2x80x9d) was determined at 200% elongation on the first cycle and is reported in the Tables in deciNewtons per tex. Unload Power (xe2x80x9cUPxe2x80x9d) was determined at 200% elongation on the fifth cycle and is reported in the Tables in deciNewtons per tex. Percent elongation at break (xe2x80x9cEbxe2x80x9d) was measured on the sixth extension cycle.
Percent set was determined as the elongation remaining between the fifth and sixth cycles as indicated by the point at which the fifth unload curve returned to substantially zero stress. Percent set was measured 30 seconds after the samples had been subjected to five 0-300% elongation/relaxation cycles. The percent set was then calculated as % Set=100(Lfxe2x88x92Lo)/Lo, where Lo and Lf are the filament (yam) length, when held straight without tension, before (Lo) and after (Lf) the five elongation/relaxation cycles.
All whiteness retention tests were performed on fiber which had been scoured and mock dyed as follows. Cards wound with spandex were immersed in a bath containing 1.5 grams of DUPONOL EP (sold by Witco, Memphis, Tenn.) per liter of water. The bath was then heated to boiling where it remained for 1 hour. The cards were then rinsed with water and put into a bath containing water adjusted to pH=5 with dilute phosphoric acid (further adjusted with dilute sodium hydroxide if necessary), and the bath was heated to boiling. The cards remained in this bath for 1 hour (mock dye) and were then rinsed with distilled water. After air-drying, the b-values of the cards were measured and recorded as the original, scoured xe2x80x9cb-valuexe2x80x9d. The cards were then exposed to fume, UV, NO2, and thermal tests substantially as described in U.S. Pat. No. 5,219,909, which is incorporated herein by reference. The changes in xe2x80x9cb-valuexe2x80x9d are reported in the Tables below, as xe2x80x9cdelta bxe2x80x9d.
To measure heat-set efficiency (xe2x80x9cHSExe2x80x9d), the yarn samples were mounted on a 10 cm frame and stretched 1.5xc3x97. The frame (with sample) was placed in an oven preheated to 175xc2x0 C. or 190xc2x0 C. for 90 seconds. The samples were allowed to relax and the frame to cool to room temperature. The samples (still on the frame) were immersed in boiling water for 30 minutes. The frame and samples were removed from the bath and allowed to dry. The length of the yarn samples was measured, and heat set efficiency was calculated according to the following formula:       %    ⁢          xe2x80x83        ⁢    HSE    =            [                                    Heat            ⁢                          -                        ⁢            set            ⁢                          xe2x80x83                        ⁢            length                    -                      Original            ⁢                          xe2x80x83                        ⁢            length                                                Elongated            ⁢                          xe2x80x83                        ⁢            length                    -                      Original            ⁢                          xe2x80x83                        ⁢            length                              ]        xc3x97    100  